A cartridge includes a cleaning unit. A casing having a wall that is formed with at least one opening that allows communication between an interior and an exterior of the casing. The cleaning unit is accommodated in the casing and that confronts the wall with a space being formed between the cleaning unit and the wall. At least a part of the cleaning unit confronts the at least one opening. The at least a part of the cleaning unit is in communication with the exterior of the casing via the at least one opening.